The present invention relates to color matching and more particularly to color matching predictability methods and systems.
Those concerned with the development of colored products, such as paints, plastics, printing inks, textiles, and the like, have long recognized the need for improved methods of faithfully reproducing color at an economical cost and in shorter times. Increasingly, manufacturers concerned with the quality and cost of color have turned to computer color control systems, which couple the precision and reliability of a spectrophotometer with the power of a digital computer to provide capabilities of color measurement, formulation, and control.
When used for color matching, such computer systems perform the function of analyzing the color sample and calculating a best match in the form of output data listing a color formulation, i.e., a proportional combination of colorants, that may be used to prepare the desired color. Although such systems usually produce a reasonably close color match, they are not entirely satisfactory because the sample and the best computer-produced match are often significantly different. In many cases color duplication is impossible. For example in a printing process, inability to duplicate a color may be due to the printed substrate, lack of clean inks in the ink system used, color saturation of a swatch, etc.
More specifically, assume a color match between a color sample on one substrate, e.g. light yellow on bright white bond paper, is to be reproduced for application on a significantly different substrate, e.g. an aluminum can, using any combination of a given number of specific ink colorants. A typical color matching computer system will read the color sample and produce an output formulation as a listing of the specific proportional combination of the ink colorants. In order to accomplish this, stored in the computer will be a data base including colorant data related to the available colorants and substrate data related to standard substrates. A computer algorithm, using the input color sample data and the stored data base, will compute the resulting proportional combination of colorants. In the example where a sample of light yellow on bright white bond paper is to be color matched on an aluminum substrate, the computer output formulation might be 10% dark yellow, 5% bright yellow, 0.2% neutral black and 84.8% opaque white. Additionally, the computer output will also include an index number as a measure of the quality of the color match, i.e. an indication of the difference between the color sample and the color producible by the computer generated formulation.
In general, given only the index number, it would not be clear to a user, at least subjectively, just how much of a difference there would be between the color sample and the finished product. In order to clearly visualize the quality of a match, a particular combination of computer output colorants must be physically mixed and applied to the particular substrate involved. As such, users are often forced to resort to complex color proving procedures, wherein actual substrates and color mixtures are prepared in search of an acceptable match. In many other cases, the value of the index number will fall outside an acceptable range, thereby rendering the corresponding formulation of no value even as a starting point in a color proving procedure.
Reducing the time involved in trial and error formulating and manual preparation of physical samples has been one of the most critical problems confronting developers of color matching systems. Consequently, those concerned with the development of color matching systems have recognized the need for a color match system that will significantly reduce costs by providing a system capable of producing information significantly more meaningful than an abstract index number, but less time consuming to perform than conventional manual color proving procedures. The present invention fulfills this need.